Published: Sat, March 18, 2017
Research | By Jennifer Evans

Google Guetzli - a new open source JPEG encoder

Google Guetzli - a new open source JPEG encoder

Smaller file sizes might seem an arcane technology concern, but they're crucial to fast-loading websites. For those companies storing and serving these images, the desire is to keep the images as small as possible.

There is, as always, a catch to using this new encoder. Smaller files are achieved by blurring together pixels that are similar, but only just enough to not distort the overall image's structure. Google Research's Zurich office led the new project, and that's why the name is Guetzli.

Google's new open source image compression algorithm is capable of reducing the size of JPEG files by 35 percent, without compromising image quality too much, and the results it produces are compatible with all web browsers and image editing software. That's important, as it means the algorithm can be used everywhere without anything else having to change. Other attempts at making images smaller have all relied on building new image formats that never get broad enough support to actually take off. Uncompressed original on the left.

The underlying compression algorithms behind popular implementations of JPEG have always been lossy; once a web version has been generated from a high-quality original master, the lost pixel information can not be recovered (except, arguably by AI - another field of interest for Google's image researchers). The algorithm used by the company allows it to compress JPEGs by up to 35% more than now available methods.

"The visual quality of JPEG images is directly correlated to its multi-stage compression process: colour space transform, discrete cosine transform, and quantization", wrote Google.

In fact, Google claims that its research shows that even when image file sizes are the same (meaning the libjpeg files are encoded in a higher quality setting, resulting in larger file sizes), human raters like the Guetzli images better.

Google says its Guetzli compression produces JPEG images with fewer photo-degrading artifacts.

The smaller images will enable web pages to load faster and use less data. If that's not something you care about, you can head over to the Github destination instead and check out all the files, instructions on installing the tool, and the code necessary for using it.

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